1. Field of the Invention
The invention relates generally to pumps, and more particularly, to the suction and discharge valves of reciprocating pumps. Still, more particularly, the invention relates to apparatus and methods that enable access to suction and discharge valves of reciprocating pumps and closure of chambers which contain them.
2. Background of the Technology
Reciprocating pumps are used in various applications. For example, reciprocating pumps are often used in drilling operations to pressurize a slurry mixture of solids and liquids known as drilling mud, which is then conveyed to the bottom of a borehole drilled in the earth. The pressurized mud is used to maintain appropriate borehole pressure, lubricate and cool a downhole drill bit, and carry loosened sediment and rock cuttings from the borehole bottom to the surface. At the surface, the cuttings and sediment are removed from the returning drilling mud, and the filtered drilling mud may be recycled and pumped back to the borehole bottom.
Suction and discharge valves are used in reciprocating pumps to control the flow of fluid into and out of the pump's cylinders where the fluid is pressurized. Due to the highly abrasive nature of the particles often present in the fluid, the valves and seals of the pumps must be designed to resist harsh abrasion, while maintaining positive sealing action under relatively high operating pressures. Even so, the valves have a finite service life, and ultimately must be replaced due to deterioration of the elastomeric sealing element of the valve, deterioration caused by erosion of the mating metal contact surfaces of the valve and valve seat, or combinations thereof. When leakage through the valves is sufficient to render the pump unable to maintain satisfactory fluid pressure for the drilling conditions, the valves must be replaced.
Maintenance of these valves is a time consuming and difficult process that presents risks of injuries to service personnel. To service most conventional valves, the valve cover is removed. In some pumps, a threaded ring acts as a valve cover retainer to hold the valve cover in place. This valve cover retainer may have through-holes that allow a pipe to be inserted and used as a lever arm to facilitate rotation and removal of the retainer and, subsequently, removal of the valve cover held by the retainer. Sometimes, a heavy sledge hammer must be used against the lever arm to loosen the valve cover retainer. Once loosened the mechanic must then unscrew and disengage the relatively long length of threads between the valve cover retainer and its seat. Furthermore, the maintenance of most conventional valves is often costly since the pump must be shut down during such maintenance procedures, thereby interrupting the drilling activity. Accordingly, there remains a need to develop apparatus and methods for safely and quickly providing access to suction and discharge valves of reciprocating pumps.